Characters as Adaptive and Specific. 265 



may originally have been useful specific characters. 

 It can scarcely be questioned that the transmuta- 

 tion of a species into a genus must, as a rule, have 

 allowed time enough for a newly acquired — i.e. 

 peculiar specific-character — to show some signs of 

 undergoing degeneration, if, as supposed, the original 

 cause of its development and maintenance was with- 

 drawn when the parent species began to ramify into its 

 species-progeny. Yet, as Darwin says, " it is notorious 

 that specific characters are more variable than 

 generic^.'' So that, upon the whole, I do not see 

 how on grounds of general reasoning it is logically 

 possible to maintain Mr. Wallace's distinction between 

 specific and generic characters in respect of necessary 

 utility. 



But now, and lastly, we shall reach the same 

 conclusion if, discarding all consideration of general 

 principles and formal reasoning, we fasten attention 

 upon certain particular cases, or concrete facts. 

 Thus, to select only two illustrations within the 

 limits of genera, it is a diagnostic feature of the 

 genus Equus that small warty callosities occur on 

 the legs. It is impossible to suggest any useful 

 function that is now discharged by these callo- 

 sities in any of the existing species of the genus. 

 If it be assumed that they must have been of 

 some use to the species from which the genus 

 originally sprang, the assumption, it seems to me, 

 can only be saved by further assuming that in existing 

 species of the genus these callosities are in a vesti- 

 gial condition — i. e. that in the original or parent 

 species they performed some function which is now 



' Origin of Species, p. 132. 



